[Immunoallergic reactions of drug origin: epidemiologic and clinical data].

Allergic and pseudoallergic reactions frequently occur in hospitalized patients and represent up to one-third of adverse drug reactions. Allergic reactions are unpredictable reactions, related to immunologic mechanisms. Pseudoallergic reactions mimic allergic reactions but no drug-specific antibody or T-cell proliferation can be demonstrated. Clinical presentations are numerous and heterogeneous, from a mild urticaria to a dramatic anaphylactic shock and an extensive bullous skin disease. A true diagnosis is rarely set up and the tools for it are lacking. In this review, we will focus on some epidemiological data concerning these reactions, including data on incidence, mortality and cost.